The invention relates to an injection mold.
Injection molds are known which have two die plates and at least one backing plate which is held between these die plates, the injection moldings produced being held in the backing plate after the mold is opened. To eject the moldings from the backing plate the mold must be opened so wide that from the outside an ejector plate on which ejector pins are located can be inserted between the backing plate and one die plate. After placement of the ejector plate, the backing plate is moved against the ejector plate with the pins, the injection moldings being pressed by the pins out of the backing plate. Thereupon the backing plate must again be moved forward to be able to move the ejector plate out of the mold. Then the mold is closed again. The described processes dictate a relatively high cycle time since on the one hand the mold must be opened relatively wide to create enough space for collision-free insertion of the injector plate and also insertion and removal of the ejector plate due to the very large stroke takes a large amount of time.
The object of the invention is to devise a generic mold in which the cycle times can be shortened.
In the invention the ejectors are no longer attached to an ejector plate, but directly to a die plate. The ejectors are offset laterally to the mold cavities in the backing plate, i.e. the ejectors in the closed state of the mold lie next to the mold cavities.
To eject the injection moldings then it is simply necessary to open the mold so far or to raise the backing plate so far from the die plate with the ejectors that they are free, to push the die plate by the relatively small amount of the lateral offset of the ejectors relative to the mold cavities and to withdraw the backing plate, by which the ejectors are pushed into the mold cavities on the backing plate and the injection moldings are ejected. It is apparent that the lift paths which are necessary in the mold as claimed in the invention for ejecting the injection moldings are much smaller than in the prior art so that the cycle times can be greatly shortened.
Basically two versions for placing the ejectors on the die plate are preferred. On the one hand, it is possible for the ejectors to be pins which are rigidly attached to the die plate and for there to be recesses for the pins on the backing plate and optionally on the second die plate. But on the other hand it is also possible for the ejectors to be pins which are movably held in the die plate elastically in the direction of motion of the backing plate.
The first embodiment has the advantage that the ejectors are attached to the die plate in a relatively simple manner. To do this it is necessary to provide recesses for the ejectors in the backing plate and, depending on the length of the pins, optionally in the opposite die plate; the pins are held in the recesses when the mold is closed.
In the second embodiment, recesses in the backing plate and the opposing die plate are not necessary; for this reason a somewhat higher cost for the elastic support and guidance of the pins in the die plate must be tolerated.